This study will evaluate the safety of a novel RNA based therapeutic AVI-7100. Beginning with a low single-dose, subjects are randomized to receive either AVI-7100 or placebo and evaluated on Study Days 0, 1, 2, 4, 10, 28. The safety and tolerability is evaluated using symptoms, clinical laboratory tests, ECG, and pharmacokinetics. Utilizing a series of stopping rules and a medical monitor, the dose will be escalated as safety and tolerability are established. Once the maximum tolerated dose (MTD) is established in the first part of this study (either limited by adverse effects or up to maximum anticipated dose), the safety and tolerability of multi-dose administration will begin (replicating anticipated clinical use). Subjects again are randomized to either AVI-7100 or placebo daily for 5 days, and evaluated on Study Days 0, 1, 2, 3, 4, 5, 6, 8, 14, and 32. The dose used in the multi-dose cohorts will also be escalated as safety and tolerability are established.